Hardened photographic film of improved photographic properties



April 1, 1952 R HARRlMAN 2,591,542

HARDENED PHOTOGRAPHIC FILM OF IMPROVED PHOTOGRAPHIC PROPERTIES Filed D60. 16, 1948 Silver halide emulsion comprising /l 2,4d|hydroxybenzaldehyde 3 llllllllllllllllllIlllllllllllllllllllllll \weight organic hardening agent Support Silver halide emulsion comprising 2,4dihydroxybenzaldehyde Fig. l.

Colloid layer containing a low molecular weight organic hardening agent Gelatin-sub Support Colloid layer containing a low molecular weight organic hardening agent Silver halide emulsion comprising 2,4-dihydroxybenza|dehyde Gelatin-sub Support Silver halide emulsion comprising 2,4-dihydroxybenzaldehyde Gelatine-sub Support Colloid layer containing a low molecular weight organic hardening agent Silver halide emulsion comprising INV ENTOR Benjamln R. Harrlman Patented Apr. 1, 1952 HARDENED PHOTOGRAPHIG FILM F IM- PROVED PHOTOGRAPHIC PROPERTIES Benjamin B. Harriman, Binghamton, N. Y., as-

signor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application December 16, 1948, Serial No. 65,568

6 Claims.

This invention relates to photographic film, and especially to a photographic film in which the gelatino silver-halide emulsion layer is not subject to the deleterious efiects of hardening agents such as after-hardening.

In the preparation of photographic gelatin dispersions and gelatino silver-halide emulsions, it has been the practice to treat the dispersions and emulsions, prior to coating, with a hardening agent so as to reduce the tendency of the gelatin to soften,-or to distend during processing of the photographic material containing the gelatin, particularly at temperatures higher than the temperature specified for processing the particular photographic material.

Compounds which have been used for hardening gelatin as such or in silver-halide emulsions are formaldehyde, hydroxy aldehydes, acrolein, glyoxal, ketoaldehydes, aminoaldehydes, and derivatives thereof, and mixtures of an aliphatic aldehyde with an aromatic compound contain ing at least one nuclear hydroxy substituent group such as phenol, resorcinol, resorcylic aldehyde, and the like. Although formaldehyde and hydroxy aldehydes are satisfactory as hardening agents, these compounds possess the undesirable property of producing excessive fog, desensitization, or flattening of gradation in the processed film.

Any hardeners that function by the liberation of formaldehyde will also have these deleterious effects as well as that of after-hardening, i. e..- hardening continues over a period of time after the film has been coated, and may surpass in degree the initial hardening on first drying. Although aliphatic aldehydes in combination with hardening modifiers-i. e., chemical compounds, such as aromatic derivatives containing at least one nuclear hydroxy substituent that have little or no hardening action per se but have a profound infiuence in affecting. the rate and degree of hardening achieved by the conventional hardening agents-diminish after-hardening and reduce fog, they invariably cause loss in speed and gradation. so that one has to make a compromise between hardening and speed. Moreover, when aliphatic aldehydes in combination with hydroxybenzenes are added to photographic emulsions, or any photographic hardening agent is added to an emulsion by itself, the hardening of, the coated film is not uniform throughout a coating obtained from any given melting kettle.

It has been proposed to harden photographic emulsions by mixing uniformly therewith an organic hardening agent and ZA-dihydroxybenzaldehydewith or without the presence of a hydroxybenzene as the hardening modifier to-obtain better hardening with less loss in photographic quality and with less; after-hardening.

Although this process has certain advantages over prior art methods of hardening gelatino silver-halide emulsions, it has certain procedural disadvantages. For example, in hardening the gelatino silver-halide emulsion, a polyhydroxybenzene and the organic hardening agent, such as formaldehyde, are added to the warm melted emulsion before coating. When the formaldehyde enters the melt, unless an impractical high dilution is used, a brief but excessive concentration is present and ready to react unfavorably on the warm emulsion. Even when the formaldehyde and the polyhydroxybenzene are uniformly distributed throughout the melt, some unfavorable effects in the photographic quality of the emulsion occur within the melt as it is held at an elevated temperature. Thus, the first coatings from a kettle containing a hardened emulsion are different from the last coatings made from the same kettle.

It is an object of the present invention to provide photographic film in which the gelatino silver-halide emulsion layer is completely hardened, by the diffusion of a low molecular weight organic hardening agent contained in gelatin or other colloidal layer adjacent to the emulsion layer, and which is not subject to the phenomenon known as after-hardening.

Another object is to provide a gelatino silverhalide emulsion which will be resistant to relatively high processing temperatures without reticulation, fogging, loss of speed, and loss of gradation.

A further object is to provide photographic films which are uniform throughout in hardness, aging characteristics, and photographic properties.

A still further object is to provide gelatino silver-halide emulsion layers, differentially hardened in. a direction perpendicular to its support, and which will swell uniformly in a direction perpendicular to the support when brought in contact with processing solutions.

Other objects and advantages will become apparent from the following description.

The foregoing objects are accomplished, according to the present invention, by incorporating in the gelatino silver-halide emulsion ZA-dihydroxybenzaldehyde (resorcylic aldehyde), with or without the presence of an aromatic compound containing at least two nuclear hydroxy substituent groups, hereinafter referred to as a polyhydroxybenzene, such as, 1,3-benzenediol (resorcinol), phloroglucinol, methylphloroglucinol, pyrogallol, 1.2,4 hvdroxybenzene (hydroxyhydroquinone), and the like or mixtures thereof. The gelatino silver-halide emulsion layer is then coated on any suitable film base having a gelatin or colloidal layer integral therewith, or it may be coated over a gelatin'or colloidal layer, or a gelatin or colloidal layer may be coated over the emulsion layer. The gelatin or other colloidal layer, hereinafter referred to as colloid layer, contains an organic hardening agent of a low molecular weight, i. e., of not more than 6 carbon atoms, which is readily difiusible through the film support, or the gelatino silver-halide layer, or the colloidal layer superposed between the film base and silver-halide emulsion layer. Organic hardening agents of low molecular weight are, for example, paraformaldehyde (polyoxymethylene), acetaldehyde (aldol), glyoxal, pyruvic aldehyde, nitromalonic aldehyde, mucochloric acid, trimethylolmelamine and the like. Th latter labile compound or polymer, which is an addition product of formaldehyde and melamine, and sold on the open market under the trade name Tanak MRX, behaves like a hardening agent. Instead of incorporating the trimethylolmelamine into the film base, or into the colloidal, subbing or surface layer, it may be coated upon the emulsion layer per s from an aqueous solution to leave a polymeric transparent film on the emulsion layer.

In these ways, the organic hardening agent in the support, gelatin subbing or colloidal layer is only brought into contact with the gelatino silver-halide emulsion layer in a sufiiciently dilute state to prevent localized deleterious reactions with the gelatin and silver halide emulsion. In addition, all coatings of a kettle or batch of th gelatino silver-halide are subjected to the same amount of hardening for the same period of time and at the same temperature thereby insuring uniform quality throughout the film.

The colloidal dispersing agent for the diffusibl hardening agent may be gelatin or other colloid such as water-soluble cellulose derivatives, e. g., hydroxyethyl cellulose, methyl cellulose, carboxyhydroxy cellulose, low acetyl value cellulose acetate, polyvinyl alcohol, partially hydrolyzed cellulose acetates and the like. If a dispersing medium other than gelatin is employed it may be coated over the gelatin subbing layer over which the usual gelatino silver-halide emulsion is coated or it may be coated directly on the gelatino silver-halide emulsion layer.

It appears that the 2,4-dihydroxybenzaldehyde in the gelatino silver-halide emulsion layer functions to boost or accelerate the hardening action of the hardening agent when it diffuses from the support or any layer and comes in contact with the gelatino silver-halide emulsion layer. The 2,4-dihydroxybenzaldehyde is, in short, a necessary element in the photographic film since without it not only does the phenomenon of after-hardening" manifest itself, but in addition the photogfaphic characteristics are rendered inferior. The contact of the diffusing organic hardening agent with the aforesaid benzaldehyde derivative is adequate where hardening without "after-hardening concomitant with retention of the desired photographic properties is desired. This is particularly true where the hardness is desired in a gelatin layer other than that hearing the photographic sensitive elements, 1. e., silver-halides. However, I have found that where it is desired not only to effect hardening without "after-hardening and simultaneously to improve markedly the photographic properties of the involved gelatino silver-halide emulsion layers, as regards their stability with respect to speed, and graduation upon long storage and incubation, it is advisable to also add with the aforesaid benzaldehyde derivative a polyhydroxybenzene such as those given above. The particular role played by the polyhydroxybenzene is not ascertainable, but is undoubtedly attributed to a mutual interaction of the diifused organic hardening agent and the 2,4-dihydroxybenzaldehyde.

The quantities of the ingredients, i. e., 2,4-dihydroxybenzaldehyde and a polyhydroxybenzene in the gelatino silver-halide emulsion, may vary depending upon the degree of hardness desired, but it is recommended that the ratio of polyhydroxybenzene to the 2,4-dihydroxybenzaldehyde be from 1:20 to 120.2. In non-curling layers and anti-halation or anti-abrasion layers, I prefer to use from .5% to 7% of any one of the aforesaid organic hardening agents in the gelatin or other colloidal layer based on the dry weight of the gelatin or other colloidal dispersing agent in the composition. In gelatinous silver-halide emulsion layers, I prefer to use from 0.25% to 2.5% of total polyhydroxybenzenes based on the dry weight of the gelatin. In these concentrations efiective hardening of the gelatino silverhalide emulsion layer is obtained without afterhardening," i. e., the melting point of the gelatin in the silver-halide emulsion-layer does not vary with time or with long periods of storage prior to actual use and processing of the photographic material.

In hardening gelatin emulsions which are neutral or slightly alkaline, i. e., emulsions having a pH greater than '7, generally between 7 and 8.5, the amounts of the low molecular weight organic hardening agent in the gelatin subbing or separate colloidal layerand the amounts of 2,4-dihydroxybenzaldehyde employed in the gelatino silver-halide emulsion layer are the same as for the non-curling, anti-halation layer, etc., and the amount of a polyhydroxybenzene in the gelatino silver-halide emulsion layer may vary from 0.005% to 5% based on the weight of the dry gelatin in the emulsion.

From the foregoing listings of polyhydroxybenzenes, I prefer to use resorcinol in conjunction with 2,4-dihydroxybenzaldehyde for the following reasons: (1) it is inexpensive, (2) it can be obtained in such a state of high purity that it does not stain gelatin, and (3) it can replace the more expensive 2,4-dihydroxybenzaldehyde to about -90% without impairing the additional hardening boost that ZA-dihydroxybenzaldehyde imparts to the organic hardening agent. In addition to these properties, resorcinol has a stabilizing effect all of its own, and if used alone in the gelatino silver-halide emulsion layer, it gives an appreciable hardening boost but not of the magnitude given by 2,4-dihydroxybenzaldehyde or in a mixture with 2,4-dihydroxybenzaldehyde.

Where it is desired to increase the gradation of a gelatino silver-halide emulsion, I prefer to use phloroglucinol in conjunction with ZA-dihydroxybenzaldehyde.

The various methods of applying the gelatino silver-halide emulsion layer to a support or colloidal layer containing an organic hardening agent will now be described with reference to the accompanying drawing.

In the accompanying drawing, Figs. 1 to 5 inclusive represent sectional views of a film provided with a gelatino silver-halide emulsion layer comprising 2,4-dihydroxybenzaldehyde and a separate layer or support containing a diffusing organic hardening agent in accordance with the present invention.

As shown in Fig. 1' a film base i of a trans above.

parent material such :as cellulose organieacetate, for example, cellulose acetate, cellulose .formate.

is coated with the usual gelatin subbing-layer 4 layer, may be applied to a film base I opposite to that in the usual gelatin subbing-layer 4, and light-sensitive layer 3 as shown in Fig. 4.

In Fig. 5, the support I, to which has been added one or a mixture of the diffusing organic hardening agents referred to above, is coated with the usual gelatin subbing-layer 4. Over this subbing-layer is .coated a light-sensitive emulsion layer 5 comprising ZA-dihydroxybenzaldehyde.

The diffusing low molecular weight organic hardening agent is incorporated into the film support during its manufacture, i. e., during the casting of the film support by dissolving the hardening agent in the cellulose ester solution.

As pointed out above, the hardening agent need not be incorporated into any one of the separate colloid layers as such. Itmay for such purposes be introduced as a labile compound or complex which will slowly break down to liberate the hardening agent. Thus, trimethylolmelamine may be applied as such to a film base opposite to that hearing the usual light-sensitive emulsion, in an anti-static surface layer as shown by 5 in Fig. 4, or over the light-sensitive emulsion layer as shown by 5 in Fig. 3. An advantage of this procedure is that it is not necessary to apply an additional hardening layer.

The advantage in employing any one of the foregoing variations listed by Figs. 1-5 is the very low temperature at which the diffusion of the organic hardening ,agent to the gelatino silyer-halide emulsion layer takes place. The very low concentration of hardening agent as it permeates the emulsion layer and the continued presence of the 2,4-dihydroxybenzaldehydewith or without a polyhydroxybenzene all aid .in f recluding deleterious effects which other-wise would take place in the light-sensitive emulsion layer. As previously pointed out, the hardening modifiers, i. e., 2, i-dihydroxybenzaldehyde and polyhydroxybenzenes exhibit a synergistic effect with I the hardeners in obtaining greater, more rapid, and more complete hardening than was possible with the hardening agents alone.

A liquid or gaseous film may be applied to the gelatino silver-halide emulsion layer to effectumarked as Bl, B2 and B3.

ate thedesiredresults. .By this procedure, a suflficient amount of the hardening agent will diffuse into the gelatino silver-halide emulsion layer to bring the desired hardening. In such a case, it is only necessary to :modify the surface tension characteristics of the gelatino silverhalide emulsion layer so that the greatest degree of accuracy be achieved in the limited time of contact such process offers in commercial practice.

The following examples illustrate several of the various methods of operation of hardening the gelatino silver-halide emulsion layer and it will be understood that these examples merely represent the preferred embodiments and are not to lie-considered as :limitative.

Example I To 5 kilograms of a melted photographic silverhalide emulsion containing 8-10% gelatin there were added an aqueous solution of 0.5 gram of 2,4-dihydroxybenzaldehyde and 4.5 grams of resorcinol and the mixture heated to and held at C. for several hours. The emulsion was then coated on a cellulose acetate film base and divided into three sections marked Al, A2 and A3. A similar emulsion but containing no hardening modifiers was coated on a cellulose acetate film base and divided into three sections and The first sections of Al and BI were left untreated. The second sections A2 and B2 were passed through a chamber containing gaseous formaldehyde and the third sections A3 and B3 were each passed through a 2% aqueoussolution of formaldehyde after the emulsion layer was chilled and set. After drying the sections of the film were compared photographically and physically. The untreated sections of Al and Bi had melting points 5-10 0. lower than any of the other emulsions, but were equal to the others in speed and gradation. However, in comparing A2 with B2, and A3 with B3, all the A examples showed substantially less fog, greater hardness, gradation and speed.

Example II Emample III To 1 kilogram of a melted ammonia type photographic silver-halide emulsion containing 23-10% of gelatin there were added 0.9 gram of resorcinol and 0.1 gram of 2,4-dihydroxybenzaldehyde, and

" the mixture heated to and held at -50" C. for

several minutes. A cellulose acetate-propionate sheet was coated with a thin layer'of this emulsion mixture and dried at room temperature. Immediately afterdrying, the emulsion layer was overcoated with a clear gelatin layer containing l5-gramsof formaldehyde per kilogram of gelatin. The resulting film (1) was compared with one (2) prepared from the same ammonia type silverhalide emulsion containing no resorcinol and 2,4-dihydroxybenzaldehyde and over which was 7 coated a gelatin layer containing 15 grams of formaldehyde per kilogram of gelatin with the following results:

Freshly Coated g at Film Fog M. P. Fog M. P.

1 0.14 60 0.--. 0. 34 58 0. 2 0.1a 36 0--.. 0.76 as" 0.

&

Example IV Example III was repeated with the exception that the formaldehyde in each of the gelatin layers of the two films was replaced by '15 grams each of glyoxal per kilogram of gelatin. The following results were obtained:

Freshly Coated g at Film Fog M. P. Fog M. P.

l 0.16 54 C 0.34 53 C. 2 l. 0. 18 43 C 0.67 47 C.

Example V To liters of the acid type emulsion of Example I there were added 1 gram of glyoxal, 1 gram of 2,4-dihydroxybenzaldehyde, and 9 grams of resorcinol, and the mixture kept at 45 C. for several hours. A cellulose acetate sheet was coated with a thin layer of this emulsion mixture, chilled and allowed to set. Immediately thereafter the moist emulsion layer was overcoated with a clear gelatin solution containing 1 kilogram of gelatin and 5 grams of glyoxal dissolved in 33 liters of water.

The resulting film (1) was compared with one (2) prepared from the same acid emulsion but containing no glyoxal and over which was coated a gelatin layer containing 19 grams of formaldehyde and 1 kilogram of gelatin dissolved in 33 liters of water. Film (2) showed substantially less fog, greater speed and higher gradation in addition to improved storage stability. Moreover, film (2) which showed uniform photographic properties throughout its entire length could be processed at 43 C., whereas film (1) melted and separated from the film base at 33 C.

From the foregoing examples, it is clearly apparent that the hardening of the gelatino silverhalide emulsion layer by the diffusion of the hardening agent in the support or adjacent gelatin or colloid layer leads to the production of a photographic film in which the gelatino silver-halide layer has an appreciable increase in melting point, maximum processing temperature, and good photographic stability on aging, and is not subject to the deleterious effects of hardening agents such as after-hardening.

Since the presence of the diiiusing organic hardening agents tends to uniformly harden the gelatino silver-halide emulsion layer whether they are incorporated directly into the support, added to a separate gelatin or colloid layer or substratum layer, it is understood that the term adjacent layer as employed herein and in the appended claims, is used in a generic sense to include each of these possible applications. It is also understood that the term colloid layer as employed herein and in the appended claims is used in a generic sense to include gelatin and the water-permeable and soluble colloidal dispersing mediums referred to above, but not the gelatino silver-halide emulsion layer.

I claim:

1. A photographic material comprising a support carrying a gelatino silver-halide emulsion layer containing at least one ofthe compounds of the group consisting of 2,4-dihydroxybenzaldehyde and a polyhydroxybenzene, said material having a layer integral therewith and adjacent to said silver-halide emulsion layer containing a low molecular weight organic hardening agent.

2. A photographic film containing a gelatino silver-halide emulsion layer having improved resistance to reticulation comprising a support, a gelatino silver-halide emulsion carried there by, said film having a colloid layer integral therewith and independent of said silver-halide emulsion layer, said gelatino silver-halide emulsion containing at least one of the compounds of the group consisting of 2,4-dihydroxybenzaldehyde and a polyhydroxybenzene and said colloid layer containing a low; molecular weight organic hardening agent.

3. A photographic film containing a gelatino silver-halide emulsion layer having improved resistance to reticulation comprising a support, and a gelatino silver-halide emulsion layer carried thereby, said emulsion layer containing at least one of the materials of the group consisting of 2,4-dihydroxybenzaldehyde and a polyhydroxybenzene and said support containing a low molecular weight organic hardening agent.

4. A photographic film according to claim 1 in which the gelatino silver-halide emulsion layer contains 2,4-dihydroxybenzaldehyde and resorcinol and said adjacent layer contains formaldehyde.

5. A photographic film according to claim 2 in which the gelatino silver-halide emulsion layer contains 2,4-dihydroxybenzaldehyde and resorcinol and said independent colloid layer contains glyoxal.

6. A photographic film according to claim 3 in which the gelatino silver-halide emulsion layer contains 2,4-dihydroxybenzaldehyde and resorcinol and the support has dispersed therein trimethylolmelamine.

BENJAMIN R. HARRIMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,165,421 Sheppard et a1. July 11, 1939 2,169,513 Brunken Aug. 15, 1939 2,309,492 Albers et a1. Jan. 26, 1943 

1. A PHOTOGRAPHIC MATERIAL COMPRISING A SUPPORT CARRYING A GELATINO SILVER-GALIDE EMULSION LAYER CONTAINING AT LEAST ONE OF THE COMPOUNDS OF THE GROUP CONSISTING OF 2,4-DIHYDROXYBENZALDEHYDE AND A POLYHYDROXYBENZENE, SAID MATERIAL HAVING A LAYER INTEGRAL THEREWITH AND CONJACENT TO SAID SILVER-HALIDE EMULSION LAYER CONTAINING A LOW MOLECULAR WEIGHT ORGANIC HARDENING AGENT. 